The invention relates to a hydraulically operated toggle-type jaw crusher typically used for fracturing rocks.
The Blake or double toggle jaw crusher is commonly used for crushing rocks or the like. It is considered very efficient because the movement of the movable jaw is relatively straight towards the stationary jaw with little relative motion along the jaw surfaces, thus reducing friction caused by grinding action. This lowers the power requirements for the crusher and the jaws have a longer life. The design of double toggle jaw crushers has changed relatively little since their introduction over a century ago, other than replacing babbit bearings with massive roller bearings to reduce friction and power requirements.
One disadvantage of the double toggle jaw crusher is the reduced distance of travel at the top of the movable jaw because the top is closer to the pivot about which the jaw rotates. This makes it difficult to crush large rocks entering the top of the jaw chamber.
Another disadvantage is illustrated by the fact that most manufacturers offer two or three models of each size of jaw crusher. The different models are required because different distances of travel between the movable jaw and the stationary jaw are required for different purposes. It is also desirable to change the angle between the toggles which governs the pressure exerted by the jaws and the speed of movement of the movable jaw. When crushing very hard material, a relatively short distance of travel and a relatively flat angle between the toggles is desirable. When the materials being crushed are softer, a greater degree of movement and a larger angle is desired. These jaw crushers are typically powered by an inertial drive including an eccentric. It is not practical to change the eccentric shaft, bearings and other parts to change the crusher from one type of material to another.
The conventional jaw crushers employing large belt driven flywheels are very hazardous. The large inertia of the flywheels means that they cannot be stopped immediately in the event of accidents. Many people have been killed or maimed by falling into jaw crushers or by being caught in the flywheel or belts.
Furthermore, the action of the flywheels, counterweights and eccentric shafts creates a violent rocking motion requiring a massive base structure sufficient to take the weight of the machine and the extreme vibration due to its action.
Hydraulically operating jaw crushers have been developed as shown for example in U.S. Pat. No. 4,406,416 to Tateishi. The jaw crusher shown in this patent has a single movable jaw operated by a hydraulic cylinder connected to a lever mechanism. The stationary jaw has an upper portion which can be fixed in an optional position by advancing or withdrawing this portion of the stationary jaw horizontally.